1. Field of the Invention
The present invention relates to a disposable syringe comprising a barrel which is open at each end and in which a piston which is movable in the barrel and seals same is or can be provided, to which piston a piston rod is or can be connected; in which the barrel on its front end is provided with a needle connection, and wherein an injection needle is attached; and in which a needle guard is provided over the injection needle, the open end of the guard being detachably connected to the needle connection on the front end of the barrel.
2. Discussion of the Prior Art
Such a syringe is disclosed in Netherlands Patent Application No. 7603511 in the name of Applicants. In the syringe described in said Patent Application the needle connection consists of a needle mount, and the open end of the needle guard is connected in a clamping manner to a part of the needle mount suitable for that purpose. Such a connection of the needle guard is more clearly shown in Netherlands Patent Application No. 7401607, also in the name of Applicants. The part of the needle mount remote from the injection needle is connected to the barrel, for example, by means of riveting or shrinking. At its other end the needle mount is usually narrowed to a sleeve-like part so that an injection needle can be connected in it. The needle guard provided over the injection needle usually has a thickened open end which is connected to the sleeve-like part of the needle mount in a clamping manner. As a result of this, a sterile sealing for the needle is obtained. Of course, the sterility of the injection needle is an essential condition for using the syringe.
The syringe known from the above-mentioned Netherlands Patent Application No. 7603511 has the disadvantage that the user can not satisfactorily control the sterility of the needle. Specifically the user cannot ascertain whether the needle guard has already been removed previously or, for example, has come loose during transport and has subsequently been replaced in its original position. In other words the user is not sure of the sterility of the injection needle.
In the above-mentioned Netherlands Patent Application No. 7401607 a safety member for an injection syringe is described which has as one of its objects the elimination of the above disadvantage. The safety member described in this Patent Application is a cap having a central bore which is slid around the needle guard up to the thickened end thereof, and which has breakable elements with which it is connected to the syringe in a detachable but irreversible manner. The user of the syringe can establish at a glance by means of said cap whether the needle guard has previously been removed.
The above-mentioned safety member gives excellent satisfaction in a syringe comprising an ampoule holder or cartridge holder; such a syringe is disclosed in the above Netherlands Patent Application No. 7401607. The plastic cap can simply be connected to the plastic cartridge holder in a few points, for example, by spot-welding. However, when such a cartridge holder, which is quite an expensive component for a disposable syringe, is lacking, as in the syringe described in the above-mentioned Netherlands Patent Application No. 7603511, the connection of the safety cap to the needle holder which usually is manufactured from aluminium is substantially impossible, in particular because high requirements have to be imposed upon this connection. In fact, on the one hand the connection elements between safety cap and needle mount must not come loose during storage and transport, but on the other hand it must be possible by a very simple operation, for example a simple rotating movement, to remove the safety member for use of the injection syringe. In addition to the disadvantage that the above-mentioned safety cap is hardly suitable for use in a syringe not having a cartridge holder, the cap has additional disadvantages. A disposable syringe should be cheap and hence of a simple construction. A safety cap as described above is a comparatively expensive solution to the problem in question. Another important disadvantage is the extra operation which has to be carried out to remove the cap for use of the syringe.